<!DOCTYPE html>
<html>

<head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
    <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.bundle.min.js"></script> </head>

<body>
    <div class="alert alert-warning alert-dismissible fade show"
        role="alert">
        <strong>Holy guacamole!</strong> You should check in on some
        of those fields below.
        <button type="button" class="close" data-dismiss="alert" 
        aria-label="Close">
            <span aria-hidden="true">&times;</span>
        </button>
    </div>
</body>

</html>